The bag below is called the petite "Alistair" bag and it also comes in a larger size, which I contemplated getting. (I still might, but in a different color.) This bag fits all of my belongings and can be worn crossbody, so what more could one ask for? Since the two black bags that I currently own are somewhat dressy and not exactly cheap, this one is perfect because it can be worn casually like how I am wearing it today. I suppose it could be worn if you're somewhat dressed up too. Although I am head over heels in love with this new bag, I've also included a selection of a few other circular bags below. Most likely I'll be adding one or more to my collection in the future!
Shell: Banana Republic scallop shell here
Bag: Clare V. petite "Alistair" here and here
Shoes: BCBG similar here
Necklace and bracelet: J. Crew
Sunglasses: Prada here